When I moved my orandas into the 40 liter (right before they got to move to the current tank), Berry lost most of the color on her wen and also turned a paler red allover, I was worried she'd turn completely white! Once I moved her to the current tank with better lighting she started getting the reds back again and they even spread a little (could be thanks to the better water quality).
It could be just the way the light shines on the fish and also loss of some pigment, but it might not be as bad as it looks. Have you looked for some bulbs that enhance reds in fish? If they eat lots of vegetables it might also contribute to loss of reds, krill, carrots and color enhancing pellets will help with that